Neuroscientists have long believed that there are sensitive periods in development during which the effects of experience play a critical role. And developmental psychologists have argued for the importance of early experience in the first years of life as being critical for brain and behavioral development. Most of the neuroscience research…

Do stage-related patterns of early cognitive development reported for normally developing children also characterize at-risk and handicapped children when mental age organization of data is used? Mental age predicted Piagetian-based cognitive levels one to three but did not predict highest-level symbolic functioning in 95 handicapped children.…